In modern internal combustion engines, devices are used for the variable adjustment of valve lift curves of gas exchange valves in order to reduce the consumption of fuel and the emissions of the internal combustion engine and to have a positive influence on the torque and power of said internal combustion engine. Devices are known in this connection, by means of which the lift of the gas exchange valves can be matched to the respective operating situation. A device of this type is known, for example, from EP 0 931 912 A2. This hydraulic valve-actuating device has a camshaft, the cams of which act on a hydraulic slave cylinder of a pressure medium volume. At the same time, a master cylinder, which is actuated by the pressure medium volume, acts on the gas exchange valve. The gas exchange valve is therefore not actuated directly by the cam but rather via a pressure medium volume connected in-between. Said pressure medium volume can be changed by means of a hydraulic valve and a volume accumulator such that the lift height of the gas exchange valve can be configured so as to be variable. The pressure medium volume therefore acts as a hydraulic consumer to which and from which pressure medium is supplied and removed during operation of the internal combustion engine.
A further known device serves to displace the timing, i.e. the opening and closing times, of the gas exchange valves. By means of these devices, the phase relationship between the crankshaft and camshaft can be adjusted in a variable manner, within a defined angular range, between a maximum early position and maximum late position. Said device is integrated into a drive train via which torque is transmitted from the crankshaft to the camshaft. Said drive train can be realized, for example, in the form of a belt drive, chain drive or gear wheel drive. In addition to the camshaft, the device has a phase adjustment device which is connected to the camshaft in a rotationally fixed manner. The phase adjustment device can be designed, for example, as a pivoting motor of vane cell construction with a plurality of pressure chambers acting counter to one another. By means of pressure medium being supplied to one group of pressure chambers while pressure medium at the same time flows out of the other group of pressure chambers, the phase relationship of an impeller relative to a cell wheel of the phase adjustment device and therefore of the camshaft relative to the crankshaft can be adjusted in a variable manner. The flow of pressure medium to and from the pressure chambers is customarily regulated by means of a hydraulic directional-control proportional valve.
A device of this type is known, for example, from DE 10 2005 060 111 A1. In this embodiment, the phase adjustment device is screwed to a camshaft, which is of solid design, by means of a central screw in order to realize the rotationally fixed connection between the phase adjustment device and the camshaft.
A further device is known from DE 102 28 354 A1. In this embodiment, a cavity serving as a volume accumulator is provided within the camshaft, which is of solid design. In operating phases of the internal combustion engine, in which a sufficient amount of pressure medium is made available by a pressure medium pump of the internal combustion engine in order to operate the phase adjustment device, the volume accumulator is filled with pressure medium. If the pressure medium requirement of the phase adjustment device increases beyond the volumetric flow provided by the pressure medium pump, the volume accumulator assists the phase adjustment device.